1. Field of the Invention
The present invention relates, in general, to apparatus for distributing fluid in hydraulic motors or pumps of the radial piston type and, more particularly, to fluid distributing apparatus provided with a fluid distributing plate and a pressure plate, having the same construction on their opposite surfaces, a retaining ring, interposed between the two plates in order to form a gap in the junction between the plates, and a plate valve, fitted over a rotating shaft in the above, gap in order to rotate in the gap while retaining the state of dynamic balance.
2. Description of the Prior Art
As well known to those skilled in the art, hydraulic pumps are devices that are used for converting the mechanical force of a prime mover, such as an electric motor or an engine, into hydraulic force. Meanwhile, hydraulic motors are devices that are used for converting hydraulic force into mechanical force. The hydraulic pump and hydraulic motor have the same construction, while their power converting directions are opposite to each other.
In a typical hydraulic pump or motor, it is possible to increase power per unit weight by increasing both the actuating pressure and the number of revolutions (rpm). However, the typical hydraulic pump or motor of the radial piston type, which has a plate valve that inevitably causes remarkable frictional loss during a high speed operation, is problematic in that it is very difficult to increase the operational speed and to increase the power per unit weight. Another problem of the typical hydraulic pump or motor resides in that they often fail to maintain constant fluid flow rate and constant hydraulic pressure in a low speed operational mode.